We propose to continue the Harvard/Brown Anxiety Research Program (HARP), a unique, naturalistic, prospective, multicenter study of 478 currently active subjects with anxiety disorders, for an additional 4 years of follow-up. This will enable us to create a complete master file with a minimum of 11 years of follow-up data on all active subjects and to incorporate new assessments and data analysis methods in order to address important unanswered questions and develop a comprehensive picture of the longitudinal course and outcome of 3 common anxiety disorders: panic disorder with and without a agoraphobia, generalized anxiety disorder, and social phobia. Our specific aims are to 1) comprehensively map patterns of course for the 3 anxiety disorders; 2) examine predictors/mediating variables, such as stressful life events, depression, substance abuse, and personality disorders, associated with the course of anxiety disorders; describe medication received and investigate the mediating effect of medication on course; 4) assess the relationship between psychosocial functioning and anxiety; symptom severity; and 5) examine the utility of a dimensional approach (i.e., anxiety - and mood-related traits) in characterizing the nature and course of the anxiety disorders and comorbid depressive disorders. Subjects will be evaluated at 6 month intervals with instruments that obtain detailed information on symptom status and severity, diagnostic status, treatment received, psychosocial functioning, and other domains. Since our earlier submission we have added new assessments that measure stressful life events, underlying mood- and anxiety-related traits, and symptom severity independent of diagnosis and functioning; we have also incorporated new data analysis methods in order to answer important questions about the anxiety disorders. To have sufficient statistical power to test our hypotheses, 4 more years of prospective observation are needed. The HARP data set is unique in its large number of subjects, comprehensiveness of assessment, and length of prospective follow-up. This proposal will allow us to more completely investigate the aims and hypotheses of the previously funded grant and to add new, previously unexplored aims and hypotheses generated by findings from HARP and other investigators during the past 4 years. Continuation of HARP is expected to shed new light on clinically and theoretically important, innovative questions about a group of common and impairing disorders which have not been adequately addressed by previous research.